In the operation of brakes for bending sheet metal, such as those disclosed in U.S. Pat. Nos. 3,147,791 to Rauen et al and 3,877,279 to the present applicant, the metal to be bent is clamped at the location of the desired bend between a pair of clamping members carried at the remote ends of "C"-shaped castings. The clamping load and the bending load are both imposed on the "C"-shaped castings which must be of appreciable depth, on the order of twelve inches or more, so that the sheet metal can extend into the "throat" of the castings.
The arms of the castings and the clamping and bending means carried thereby are, in effect, cantilevered from the curved joining portions of the individual castings. As a result, excessive bending loads, as where heavy gauge sheet metal is being bent, tend to spread the clamping members by deflecting and permanently distorting the arms of the castings. Thus, severe limitations are placed on the use of conventional lightweight, portable bending brakes, and the user must be careful not to bend sheet metal of excessive thickness, lest he distort his brake sufficiently to render it incapable of subsequently clamping any sheet metal into position for bending.
Also, prior art brakes have utilized stops which are adjustable along the throat of the castings, so that the stops, when adjusted, limit the extent of insertion of the sheet metal into the throat. Typically, two such stops are provided at the extremities of the brake, and the stops are adjusted to the desired distance from the bending plane. Upon clamping of the sheet metal into position, the abutment of the sheet metal with the stops assures the bending of the sheet metal at the desired location.